This invention relates generally to a hydraulic valve lifter, and more particularly, to a hydraulic valve lifter for variable displacement engine of an automobile.
When an automobile with a multi-cylinder engine is running under low load conditions at relatively constant speed or decent of a long hill or during engine deceleration or idling performances, it is unnecessary to operate all of the cylinders of the engine. In order to save fuel consumption, or to improve gas mileage, there have been proposed various type of hydraulic lifters to effectively perform a variable displacement of the multi-cylinder engine.
One of such prior art lifter includes a valve housing, a plunger disposed within a bore of the valve housing and operatively connected to one end of a rocker arm. The plunger is slidably movable within the bore of the valve housing. When the corresponding engine cylinders are not in use due to one of the above conditions of automobile running state, working fluid (oil) of the lifter wll not generate the pressure increase, instead, just allowing the inflow/outflow of the working fluid into and out of working chamber of the lifter.
Such prior art discloses also that the diameters of the plunger and the housing bore are substantially the same, i,e., the outer diameter of the plunger being substantially equal to the inner diameter of the bore of the housing. According to such structure, the amount of hydraulic fluid flow is considerable and the slidable movement of plunger may not be effectively carried out. On the other hand, if the inner diameter of the housing bore is lessened in order to avoid the problems, the size of one-way valve therein should be reduced accordingly, which will not meet the required functions of the one-way valve.